JP4833424B2 - Rotation sensor - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a rotation sensor.
[0002]
[Prior art]
A rotation sensor that detects the rotation angle or relative rotation angle of a shaft in a non-contact manner, for example, detects torque in a steering shaft of an automobile in which two shafts that rotate relative to each other are connected via a torsion bar. A rotation sensor used for electronic control is known (for example, see Japanese Patent Publication No. 7-21433). In this type of rotation sensor, a first rotor is attached to a first shaft connected by a torsion bar, a second rotor is attached to a second shaft, and an excitation coil is attached to the first and second rotors. The fixed core is rotatably arranged inside in the radial direction, the relative rotation of the first and second shafts is detected by a change in inductance of the exciting coil, and acts between the first shaft and the second shaft. The torque to be detected is detected.
[0003]
[Problems to be solved by the invention]
By the way, the fixed core is easy to mold even in a complicated shape, and can be mass-produced in a short time at low cost. Therefore, a plastic magnet is used instead of an electromagnetic steel plate or a ferrite core as a core body for accommodating an exciting coil. It has become.
[0004]
However, since the relative permeability of the plastic magnet is smaller than that of the electromagnetic steel plate or ferrite core, there is a problem that the shape restriction is larger than that of the fixed core using the electromagnetic steel plate or ferrite core.
That is, as shown in FIG. 9, the fixed core 1 has a lead hole 1c for drawing out the lead wire of the exciting coil 1b (see FIG. 10) to the core body 1a. For this reason, as shown in FIG. 10, the core body 1 a needs to have a lead hole 1 c formed at the center in the height direction and have a vertically symmetrical shape. In the rotation sensor, unless the core body is vertically symmetrical, the magnetic circuit formed therein is not vertically symmetrical, the sensitivity (inductance) fluctuates greatly, and the rotation angle is erroneously detected. Because there is a fear.
[0005]
Thus, if the position of the lead-out hole formed in the core body of the fixed core is limited, the rotation sensor has a problem that the degree of freedom in design or use is extremely limited.
The present invention has been made in view of the above points, and even if a plastic magnet is used for the core body, the position of the lead-out hole for drawing out the lead wire is not limited, and there is no possibility of erroneously detecting the rotation angle or the like. The purpose is to provide.
[0006]
[Means for Solving the Problems]
In order to achieve the above object in the present invention, a first rotor having a plurality of nonmagnetic conductors arranged at predetermined intervals in the circumferential direction and attached to a rotating first shaft, an excitation coil, The exciting coil has a lead-out hole for leading the lead wire to the outside, and is formed into a cylindrical shape from the first rotor and a fixed core that is fixed to a fixing member at a radial interval, and an insulating magnetic material A main body, and a plurality of nonmagnetic conductor layers disposed on the main body at predetermined intervals in the circumferential direction at intervals corresponding to the plurality of nonmagnetic conductors, and the first shaft via a torsion bar And a second rotor that is connected to a second shaft that rotates relative to the first shaft and is disposed at a predetermined distance in the radial direction from the first rotor, and the relative rotation of the first and second rotors. The excitation coil Based on the inductance change, in the rotation sensor for detecting a rotational angle or the relative angle of rotation of the two shafts in a non-contact, said fixed core, with the core body is molded from plastic magnet, the inside of the ring-shaped core body A concave groove for accommodating the coil is formed on the inner peripheral surface, and a groove is formed along the circumferential direction on the inner upper surface or the lower surface of the core body .
[0007]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, as an embodiment of the rotation sensor according to the present invention, for example, a rotation sensor for detecting torque of a steering shaft transmitted from a main shaft to a driven shaft via a conversion joint (torsion bar) in an automobile is shown in FIGS. 8 will be described.
[0008]
As shown in FIGS. 1 and 2, the rotation sensor 10 includes a first rotor 11, a fixed core 12, and a second rotor 13. Here, the steering shaft 5 is connected to a wheel-side driven shaft 5c via a torsion bar 5b at a handle-side main driving shaft 5a, and the main driving shaft 5a rotates relative to the driven shaft 5c within a predetermined angle range. .
[0009]
The first rotor 11 is attached to a predetermined position in the axial direction of the main drive shaft 5a, and as shown in FIGS. 1 and 2, four sheets disposed between the flange 11a and the first rotor 11 and the fixed core 12. And a slat 11b. Each wing plate 11b is made of a nonmagnetic metal such as aluminum or copper having a shielding property against an alternating magnetic field, and is arranged on the flange 11a evenly in the circumferential direction at a predetermined central angle, for example, at a central angle of 45 °. It is formed toward.
[0010]
The fixed core 12 is arranged on the outer side of the first rotor 11 with a slight gap of about several millimeters in the radial direction between the main body 11a and a fixed member (not shown) located in the vicinity of the steering shaft 5. Fixed. As shown in FIGS. 1 and 2, the fixed core 12 is accommodated in a core body 12 a formed from the same plastic magnet as the second rotor 13, and a concave groove formed in the core body 12 a in the circumferential direction. And an exciting coil 12h.
[0011]
As shown in FIGS. 3A to 3C, the core body 12a is formed into a ring shape by an upper half body 12b and a lower half body 12c. As shown in FIG. 3B, the upper half body 12b has a cross-sectional shape formed in an inverted L shape. The lower half 12c has recesses 12d formed at equal intervals at four locations in the circumferential direction, and as shown in FIG. 3A, lead-out window portions 12i are formed, and FIGS. As shown in FIG. 3, a groove 12e is provided on the upper surface along the circumferential direction.
[0012]
The recess 12d serves as a lead-out hole for drawing out the lead wire 12f of the exciting coil 12h to the outside when the upper half body 12b and the lower half body 12c are joined. The groove 12e is provided to shield the magnetic flux flowing in the core body 12a. For this reason, as shown in FIG. 4, when the width is W, the depth is t, the height of the portion that accommodates the exciting coil 12h is H, and the height of the lead-out window portion 12i is L, as shown in FIG. W is preferably in the range of L / 2 <W <H, and the depth t is in the range of H / 10 <t <H / 2.
[0013]
Moreover, it is preferable to provide the groove | channel 12e in the surface near the derivation | leading-out window part 12i among the lower surface of the upper half body 12b, and the upper surface of the lower half body 12c.
Furthermore, the lead wire 12f is protected from disconnection due to vibration or the like during use of the rotation sensor 10 by a terminal plate 12g (see FIG. 3B) provided in the recess 12d. The exciting coil 12h is connected to a signal processing circuit (not shown) by an electric wire (not shown) extending from the recess 12d to the outside, and an alternating current is passed from the signal processing circuit. Here, as the exciting coil 12h, a bobbin in which an electric wire is wound may be used.
[0014]
The second rotor 13 is attached at a predetermined position in the axial direction of the driven shaft 5c, and as shown in FIG. 2, copper pieces 13b are alternately provided in the circumferential direction at intervals of 45 ° on the main body 13a. The main body 13a is provided with a flange 13c attached to the driven shaft 5c at the lower portion, and is formed into a cylindrical shape from an insulating magnetic material. The body 13a is made of a thermoplastic synthetic resin having electrical insulation properties such as nylon, polypropylene (PP), polyphenylene sulfide (PPS), ABS resin, etc., and Mg—Zn, Ni—Zn, or Mn—Zn ferrite. A plastic magnet in which soft magnetic material powder is mixed at 10 to 70% by volume is used. Here, the second rotor 13 may be provided with a nonmagnetic conductor on the outer periphery of the main body 13a formed into a cylindrical shape by the plastic magnet at intervals of a predetermined central angle in the circumferential direction, or may be embedded in the main body 13a. .
[0015]
In the rotation sensor 10 configured as described above, the first rotor 11 is attached to the main driving shaft 5a, the second rotor 13 is attached to the driven shaft 5c, and the fixed core 12 is fixed to the fixing member to be used in the steering device. Assembled.
In the assembled rotation sensor 10, the magnetic circuit that connects the core main body 12 a and the main body 13 a made of the plastic magnet of the first rotor 11, as shown in FIG. Flows along the CMG. As a result, the AC magnetic field crosses the plurality of blades 11b made of the nonmagnetic metal of the first rotor 11, so that an eddy current is induced in the copper piece 13b. At this time, the direction of the AC magnetic field induced by the eddy current is opposite to the direction of the AC magnetic field generated by the AC current flowing through the exciting coil 12h. As a result, the direction of the magnetic flux generated by the AC exciting current of the exciting coil 12h generated in the gap portion between the core body 12a where the wing plate 11b exists and the second rotor 13 is opposite to the direction of the magnetic flux generated by the eddy current. The magnetic flux density becomes smaller. On the contrary, in the gap portion where the wing plate 11b does not exist, the direction of the magnetic flux due to the AC exciting current of the exciting coil 12h and the direction of the magnetic flux due to the eddy current are the same, so the total magnetic flux density is increased. That is, a non-uniform magnetic field is formed in the gap portion between the core body 12 a and the second rotor 13.
[0016]
Therefore, when the first rotor 11 rotates relative to the second rotor 13, the wing plate 11b of the first rotor 11 crosses the non-uniform magnetic field, and the total amount of magnetic flux crossed by the wing plate 11b changes. The magnitude of the eddy current generated in the piece 13b changes. For this reason, in the rotation sensor 10, the impedance of the excitation coil 12 h varies depending on the relative rotation angle between the first rotor 11 and the second rotor 13.
[0017]
The rotation sensor 10 measures the impedance fluctuation of the exciting coil 12h by detecting the phase shift amount of the pulse signal, and based on this, detects the relative rotation angle between the first rotor 11 and the second rotor 13, and thus the torque.
Here, the rotation sensor 10 includes the fixed core 1 having a structure shown in FIG. 10 in which the groove 12e is not formed along the circumferential direction inside the fixed core 12, that is, the upper surface of the lower half 12c constituting the core body 12a. As shown in FIG. 5 (b), the magnetic flux generated by the alternating current flowing through the exciting coil 12h flows along the magnetic circuit CMG. It is not symmetrical in the vertical direction. Further, when the lead-out window portion 12i is arranged so as to be shifted in the vertical direction from the center portion, the magnetic circuit CMG is not significantly symmetrical in the vertical direction.
[0018]
On the other hand, in the rotation sensor 10 of the present invention, a groove 12e is formed along the circumferential direction in the fixed core 12, that is, on the upper surface of the lower half 12c constituting the core body 12a. For this reason, in the rotation sensor 10, since the magnetic flux due to the alternating current flowing through the exciting coil 12h does not flow on the groove 12e side having a low permeability, as shown in FIG. 5A, the core body 12a and the first rotor A magnetic circuit CMG that flows along the magnetic circuit CMG connecting the main body 13a made of 11 plastic magnets and is symmetrical in the vertical direction is formed.
[0019]
As a result, in the rotation sensor 10, the magnetic circuit CMG is vertically symmetric even if the core body 12a is not vertically symmetric due to the recess 12d formed in the lower half 12c. Torque can be detected correctly.
Here, the rotation sensor 10 having the width W = 2 mm and the depth t = 1 mm of the groove 12e and the height H = 3 mm of the portion that accommodates the exciting coil 12h, the width W = 1 mm, and the depth t = 0 of the groove 12e. Using the rotation sensor 10 of 5 mm and the height H = 3 mm of the part that accommodates the exciting coil 12h, the relative angle between the first rotor 11 and the second rotor 13 is set to 0 ° so that the torque becomes zero, and the first And the 2nd rotors 11 and 13 were rotated 1 time with respect to the fixed core 12, and the relationship between a rotation angle (degree) and a torque was measured. The results are shown in FIGS. 6 (a) and 6 (b). For comparison, the rotation sensor 10 not having the groove 12e and the groove 12e are not provided, and as shown in FIGS. 9 and 10, the extraction hole 1c is formed at the center in the height direction, and the upper half body and the lower half body are formed. The rotation sensor 10 having the same configuration except that the fixed core 1 is vertically symmetrical is used, and the relationship between the rotation angle (°) and the torque is measured in the same manner. The results are shown in FIGS. 6 (c) and (d).
[0020]
As is clear from the comparison of the results shown in FIGS. 6A and 6B and FIGS. 6C and 6D, when the groove 12e is formed in the fixed core 12 along the circumferential direction, It can be seen that the rotation sensor 10 has a smaller torque variation due to a change in the rotation angle (°), and the larger the width W and the depth t of the groove 12e, the more stable the change in the torque and the correct torque can be detected. .
[0021]
Here, in the rotation sensor of the present invention, if a groove is formed along the circumferential direction inside the fixed core, the fixed core 12 is arranged in two upper and lower stages like the rotation sensor 20 shown in FIG. Even if there is a disturbance such as environmental temperature fluctuation, electromagnetic noise, oscillation frequency fluctuation in the oscillation circuit, power supply voltage or assembly error, the detection accuracy fluctuation is small, and a double core type that can accurately detect torque may be used. In this case, the rotation sensor 20 arranges the first rotor 11 between the fixed core 12 and the second rotor 13 in the same manner as the rotation sensor 10.
[0022]
Further, like the rotation sensor 25 shown in FIG. 8, the core body 26a of the fixed core 26 is constituted by an upper member 26b, an intermediate plate 26c, and a lower member 26d, and the intermediate plate is similar to the lower half body 12c of the rotation sensor 10. The recesses 26e may be formed at a plurality of locations along the circumferential direction at 26c in the circumferential direction, and grooves 26f may be provided on the upper and lower surfaces along the circumferential direction. In this case, the rotation sensor 25 protects the lead wire 26h extending from the exciting coil 26g of the fixed core 26 with the terminal plate 26j provided in the recess 26e.
[0023]
Although the above embodiment has been described with respect to the case of the rotation sensor that detects torque, the rotation angle can also be detected.
In addition to the automobile steering shaft described in the above embodiment, the rotation sensor according to the present invention is for obtaining a relative rotation angle, rotation angle, and torque between rotating shafts rotating with each other, such as a robot arm. Anything can be used.
[0024]
【The invention's effect】
According to the first aspect of the present invention, it is possible to provide a rotation sensor in which even if a plastic magnet is used for the core body of the fixed core, the position of the lead-out hole through which the lead wire is drawn out is not limited and there is no possibility of erroneous detection. .
[Brief description of the drawings]
FIG. 1 is a cross-sectional front view of a rotation sensor of the present invention.
2 is a cross-sectional view taken along line C1-C1 of the rotation sensor of FIG.
3 is a front view (a), a left half sectional view (b), and a plan view (c) of a lower half of a fixed core used in the rotation sensor of FIG. 1. FIG.
4 is a cross-sectional view illustrating the shape of a groove formed in the fixed core shown in FIG.
FIG. 5 is a left half sectional view of a rotation sensor showing a magnetic circuit when a groove formed in the fixed core is present (a) and when there is no groove (b).
FIG. 6 is a torque change diagram showing the relationship between the rotation angle measured by the rotation sensor and the torque when there is a groove formed in the fixed core (a), (b) and when there is no groove (c), (d). It is.
FIG. 7 is a left half sectional view showing another embodiment of the rotation sensor of the present invention.
FIG. 8 is a left half sectional view showing still another embodiment of the rotation sensor of the present invention.
FIG. 9 is a front view of a fixed core used in a conventional rotation sensor.
10 is a left half sectional view of the fixed core of FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Rotation sensor 11 1st rotor 11a Flange 11b Blade 12 Fixed core 12a Core main body 12b Upper half body 12c Lower half body 12d Recessed part (drawing hole)
12e groove 12f lead wire 12h exciting coil 12i lead-out window portion 13 second rotor 13a body 13b copper piece 20 rotation sensor 25 rotation sensor 26 fixed core 26a core body 26b upper member 26c intermediate plate 26d lower member 26e recess 26f groove 26g excitation coil 26h Lead wire 26j Terminal board

Claims (1)

A first rotor having a plurality of nonmagnetic conductors arranged at predetermined intervals in the circumferential direction and attached to a rotating first shaft;
An exciting coil, a lead core that leads out the lead wire of the exciting coil to the outside, a fixed core that is fixed to the fixing member at a radial interval from the first rotor, and a cylindrical shape from an insulating magnetic material A plurality of nonmagnetic conductor layers disposed on the main body at predetermined intervals in the circumferential direction at intervals corresponding to the plurality of nonmagnetic conductors, and the first shaft includes A second rotor connected via a torsion bar and attached to a second shaft that rotates relative to the first shaft, and disposed at a predetermined interval in the radial direction from the first rotor;
In the rotation sensor that detects the rotation angle or the relative rotation angle of the two shafts in a non-contact manner based on the inductance fluctuation of the exciting coil due to the relative rotation of the first and second rotors,
In the fixed core, the core body is formed of a plastic magnet, and a concave groove for accommodating a coil is formed in the inner peripheral surface of the ring-shaped core body. A rotation sensor characterized in that a groove is formed along the direction .

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